Regions
Northwest Inland.
A brief return to winter in the alpine on Tuesday. New snowfall and strong southerly winds are expected to form thin new wind slabs at higher elevations.
Weather Forecast
A weak storm system is expected to reach the coast Monday overnight. 2-5cm of snowfall is forecast for Tuesday. Strong southerly winds are expected in the alpine with afternoon freezing levels around 1300m. Light snowfall may continue Tuesday overnight and should be done by Wednesday morning. A mix of sun and cloud is forecast for Wednesday and Thursday with light alpine winds and afternoon freezing levels around 1400-1500m.
Avalanche Summary
On Sunday afternoon, loose wet avalanches up to size 2.5 were reported in the far north of the region. With the arrival of spring, field observations and data have become very limited in the region. A lack of avalanche reports does not mean avalanches are not occurring. On Tuesday, thin new wind slabs may form in the alpine. Cornices have been weak recently and may fail naturally with storm loading. Loose wet avalanches are possible at lower elevations that see rainfall.
Snowpack Summary
Melt-freeze conditions are expected to be widespread except possibly on high elevation north aspects. Surface crusts are forming overnight and breaking down during the day. The snowpack's strength is directly related to the thickness and strength of these crusts. Where there are layers in the snowpack, they are generally bonding. A widespread crust/facet layer from early February and depth hoar at the bottom of the snowpack (primarily in northerly & inland areas) are dormant. Strong, thick crusts in the upper parts of the snowpack have limited the reactivity of these old layers; however, they could potentially once again produce isolated yet large avalanches with prolonged periods of warming.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.